The present invention relates to a voltage detection circuit formed as an integrated circuit device and which detects an input voltage of a predetermined level, and more particularly to a voltage detection circuit producing a detecting signal when an input voltage is larger in absolute value than a power supply voltage.
For the purpose of controlling an internal circuit operation in response to the level of an input voltage, a detection circuit is required to detect the input voltage level. For example, an electrically programmable read only memory device (hereinafter, referred as an "EPROM"), is brought into a programming operation mode when the level of a voltage supplied to a programming voltage input terminal is larger in absolute value than a power supply voltage supplied to the EPROM. There are logic circuit devices, data processing devices and/or memory devices including EPROM that have internal circuits which are placed into a test mode by supplying a predetermined terminal with a voltage larger in absolute value than a signal voltage which is supplied in an ordinary operation mode. The signal voltage supplied in the ordinary operation mode may have the same level as a power supply voltage supplied to such devices. Accordingly, a voltage detection circuit is required to detect whether or not an input voltage is larger than a power supply voltage in absolute value.
One voltage detection circuit of this type according to the prior art employs a transistor having a threshold value such that it turns ON in response to an input voltage higher than a power supply voltage, and the input voltage level is thus detected by the state of this transistor.
Another detection circuit according to the prior art utilizes a parasitic transistor formed in an integrated circuit device, this parasitic transistor being made conductive by an input voltage higher than a power supply voltage.
In both of these detection circuits, however, the manufacturing process is complicated to obtain a predetermined detection level, and it is very difficult to change the detection level.